1. Technical Field
The present invention relates to an electro-optical device having a pair of first substrate and second substrate, which are opposed to each other, and light shielding films; which are formed on the second substrate to shield light from entering corresponding transistors formed on the first substrate, and also relates to an electronic apparatus having the electro-optical device.
2. Related Art
A known electro-optical device, such as a light transmissive liquid crystal device is configured so that liquid crystal is interposed between a first substrate and a second substrate, which are formed of a glass substrate, a crystal substrate, a silicon substrate, or the like. Switching elements, such as thin-film transistors, and pixel electrodes are arranged on the first substrate in a matrix and an opposite electrode is arranged on the second substrate. Then, image display may be performed by changing the optical characteristics of the liquid crystal layer interposed between the first substrate and the second substrate on the basis of image signals.
In addition, an element substrate is the first substrate. The transistors are arranged on the element substrate. An opposite substrate is the second substrate. The opposite substrate is opposed to the element substrate. The element substrate and the opposite substrate are separately manufactured. The element substrate and the opposite substrate are, for example, formed so that a semiconductor thin film, an insulating thin film, and a conductive thin film, each of which has a predetermined pattern, are laminated on a crystal substrate. The element substrate and the opposite substrate each are formed by alternately performing a film deposition process and a photolithography process on each film in each of the layers.
Meanwhile, in the element substrate, a plurality of transistors that are provided in correspondence with pixel electrodes are formed at positions corresponding to crossover regions of data lines that supply image signals to the pixel electrodes and scanning lines that supply on signals to the transistors. The crossover regions are formed in a matrix in the display area of the liquid crystal device.
Here, when light enters known semiconductor layers in the transistors, specifically, channel regions of the semiconductor layers or regions of the semiconductor layers, which are electrically connected to pixel electrodes, the transistors malfunction and, therefore, there is a problem that display chrominance nonuniformity, cross-talk, and/or flicker occur in the liquid crystal device due to off leakage current and, in addition, defective display, such as a decrease in display contrast, occurs.
In consideration of the above problem, there is also a known liquid crystal device in which various thin films are laminated on an element substrate, and, of these thin films, light shielding films are provided in a layer formed below the semiconductor layers and cover the lower sides of the semiconductor layers in plan view, while other light shielding films are provided in a layer formed above the semiconductor layers and cover the upper sides of the semiconductor layers in plan view, thus making it possible to prevent light from entering the semiconductor layers.
For example, the scanning lines serve as light shielding films that cover the lower sides of the semiconductor layers in plan view, and the data lines and capacitor lines that hold voltages of the pixel electrodes serve as light shielding films that cover the upper sides of the semiconductor layers in plan view.
In addition, a known configuration in which, in the opposite substrate as well, in the display area, light shielding films are formed around each of the pixels in a stripe or in a matrix, which is described, for example, in Japanese Unexamined Patent Application Publication No. 2003-121879. The light shielding films, which are formed on the opposite substrate in a matrix, as described in JP-A-2003-121879, when the opposite substrate is bonded to the element substrate, are positioned so as to overlap the scanning lines and the data lines, which are formed on the element substrate in a matrix, as viewed in plan, so that the light shielding films, in cooperation with the light shielding films formed on the element substrate, prevent light from entering the transistors.
The opposite substrate, on which thin films have been laminated, is adsorbed by an adsorption head of a robot, or the like, and bonded through a seal material to the element substrate on which thin films have been laminated, with high accuracy of position.
Specifically, in order to shield light from entering the transistors by the light shielding films as well, the light shielding films, which are formed on the opposite substrate in a matrix, are bonded to the scanning lines and the data lines, which are formed on the element substrate in a matrix, in such a manner that the light shielding films overlap the scanning lines and the data lines with high positional accuracy.
However, it is difficult to bond the opposite substrate to the element substrate with completely high positional accuracy. In addition, even when the opposite substrate is bonded to the element substrate with high positional accuracy, when warpage, or the like, occurs in the element substrate or in the opposite substrate, the position of the opposite substrate may be deviated relative to the element substrate.
Furthermore, in recent years, in order to improve aperture ratio of each pixel, the widths of the light shielding films formed on each of the element substrate and the opposite substrate are made narrow to about 1.5 micrometers as compared to for example, about 2.5 to 3 micrometers in the existing art.
Thus, when the opposite substrate is bonded to the element substrate but the position of the opposite substrate is deviated relative to the element substrate, that is, when a positional deviation error of, for example, about plus or minus 0.5 to 0.7 occurs as a result of bonding of the substrates, the light shielding films formed on the opposite substrate in a matrix protrude into the light transmission regions in the display area. Thus, there has been a problem that the pixel aperture ratio varies among liquid crystal devices. In addition, there also has been a problem that the aperture ratio varies among pixels, in which some of the pixels ensure aperture ratios but other pixels have considerably decreased aperture ratios.